This invention relates generally to color imaging employed in electrography, particular to a method for automatically control mixed primary colorants to match a customer-selected color which is integrated with a color applicator, such as a xerographic printer using liquid and dry xerographic toners.
Cross reference is made to the following application filed concurrently herewith: U.S. patent application Ser. No. 09/989,669, now U.S. Pat. No. 6,526,244, entitled xe2x80x9cHybrid Electrophotographic Apparatus For Custom Color Printing,xe2x80x9d by Enrique Viturro, John F. Knapp, and Anthony Walsh.
One method of printing in different colors is to uniformly charge a charge retentive surface and then expose the surface to information to be reproduced in one color. This information is rendered visible using marking particles followed by the recharging of the charge retentive surface prior to a second exposure and development. This recharge/expose/and develop (REaD) process may be repeated to subsequently develop images of different colors in superimposed registration on the surface before the full color image is subsequently transferred to a support substrate. The different colors may be developed on the photoreceptor in an image on image development process, or a highlight color image development process (image next-to image). Each different image may be formed by using a single exposure device, e.g. ROS, where each subsequent color image is formed in a subsequent pass of the photoreceptor (multiple pass). Alternatively, each different color image may be formed by multiple exposure devices corresponding to each different color image, during a single revolution of the photoreceptor (single pass).
Electrostatographic printing systems typically develop an electrostatic latent image using solid toner particles either in powder form or suspended in a liquid carrier. In liquid developing systems, the liquid developer typically has about two percent by weight toner material distributed in the liquid carrier. An electrostatic latent image is developed by applying the liquid developer to the photoconductive member, whereby the toner particles are selectively attracted to the surface of the photoconductive member in accordance with an electrostatic latent image.
Customer selectable colors are typically utilized to provide instant identification and authenticity to a document. As such, the customer is usually highly concerned that the color meets particular color specifications. For example, the red color associated with Xerox"" digital stylized xe2x80x9cXxe2x80x9d is a customer selectable color having a particular shade, hue and color value. Likewise, the particular shade of orange associated with Syracuse University is a good example of a customer selectable color. A more specialized example of customer selectable color output can be found in the field of xe2x80x9ccustom colorxe2x80x9d, which specifically refers to registered proprietary colors, such as used, for example, in corporate logos, authorized letterhead and official seals. The yellow associated with Kodak brand products, and the brown associated with Hershey brand products are good examples of custom colors which are required to meet exacting color standards in a highlight color or spot color printing application.
The various colors typically utilized for standard highlighting processes generally do not precisely match customer selectable colors. Moreover, customer selectable colors typically cannot be accurately generated via halftone process color methods because the production of solid image areas of a particular color using halftone image processing techniques typically yields non-uniformity of the color in the image area.
Further, lines and text produced by halftone process color are very sensitive to misregistration of the multiple color images such that blurring, color variances, and other image quality defects may result. As a result of the deficiencies noted above, customer selectable color production in electrostatographic printing systems is typically carried out by providing a singular premixed developing material composition made up of a mixture of multiple color toner particles blended in preselected concentrations for producing the desired customer selectable color output. This method of mixing multiple color toners to produce a particular color developing material is analogous to processes used to produce customer selectable color paints and inks. In offset printing, for example, a customer selectable color output image is produced by printing a solid image pattern with a premixed customer selectable color printing ink as opposed to printing a plurality of halftone image patterns with various primary colors or compliments thereof.
This concept has generally been extended to electrostatographic printing technology, as disclosed, for example, in commonly assigned U.S. Pat. No. 5,557,393, wherein an electrostatic latent image is developed by a dry powder developing material comprising two or more compatible toner compositions which have been mixed together to produce a customer selectable color output. Customer selectable color printing materials including paints, printing inks and developing materials can be manufactured by determining precise amounts of constituent basic color components making up a given customer selectable color material, providing precisely measured amounts of each constituent basic color component, and thoroughly mixing these color components.
This process is commonly facilitated by reference to a color guide or swatch book containing hundreds or even thousands of swatches illustrating different colors, wherein each color swatch is associated with a specific formulation of colorants. Probably the most popular of these color guides is published by PANTONE(copyright), Inc. of Moonachie, N.J. The PANTONE(copyright) Color Formula Guide expresses colors using a certified matching system and provides the precise formulation necessary to produce a specific customer selectable color by physically intermixing predetermined concentrations of up to four colors from a set of up to 18 principal or basic colors. There are many colors available using the PANTONE(copyright) system or other color formula guides of this nature that cannot be produced via typical halftone process color methods or even from mixing selected amounts of cyan, magenta, yellow and/or black inks or developer materials.
In the typical operational environment, an electrostatographic printing system may be used to print various customer selectable color documents. To that end, replaceable containers of premixed customer selectable color developing materials corresponding to each customer selectable color are provided for each print job.
Replacement of the premixed customer selectable color developer materials or substitution of another premixed color between different print jobs necessitates operator intervention which typically requires manual labor and machine downtime, among other undesirable requirements. In addition, since each customer selectable color is typically manufactured at an off-site location, supplies of each customer selectable color printing ink must be separately stored for each customer selectable color print job.
Conventional liquid printing systems, such as liquid immersion development (LID) systems, can generate custom colors by combining two or more primary color toners before depositing the toners and then using the mixed toner to develop an electrostatic latent image. However, due to the differences in physical and chemical properties of the toners of different colors and other factors, a sophisticated feedback scheme must be used to obtain accurate color reproduction and color stability. For example, the differential mobility of the mixed toners often results in different consumption rates of different toner during development, requiring complex color control techniques to maintain a desired composition, e.g. color, of the toner and the color and density of the toner image created.
The on-demand custom color capability of electrostatographic printing systems may vary significantly due to numerous conditions affecting image development, among various factors, including but certainly not limited to the methods and apparatus used to mix the primary colors to achieve the desired custom color and the process controls implemented on the color mixing and development subsystems to maintain the color accuracy and stability. In general, a number of primary color developers are mixed in a reservoir with certain proportions according to the customer selection and the consumption rate of the primary colors, and then the developer mixture is applied to the latent image for development. Exemplary patents which may describe certain general aspects for achieving customer selectable colors, as well as specific apparatus therefor, may be U.S. Pat. No. 5,781,828 to Caruthers et al., U.S. Pat. No. 6,052,195, U.S. Pat. No. 6,049,683 as well as other patents cited therein.
There is provided a method for creating a color image representing a document in a printing machine comprising: recording a first latent image on a charge retentive surface moving along an endless path; developing said latent image with a developer unit having developer material comprising dry marking particles of a first colored; recording a second latent image on a charge retentive surface moving along an endless path; developing said second latent image with a developer unit having developer material comprising a solution liquid carrier and marking particles of a second colored.
There is also provided an apparatus for developing an image on an imaging surface, comprising: a first developer unit having dry marking particles therein for developing a first portion of the image; and a second developer unit having a solution of marking particles and liquid carrier therein for developing a second portion of the image.